1. Field of the Invention
The disclosed embodiments relate to autofocus devices and in particular to autofocus systems and methods of focusing microscope optics on a surface of a sample. The autofocus method described here uses an autofocus score related to the best focus on the surface of a sample.
2. Related Art
Autofocus methods are implemented to focus cameras including cameras imaging through a microscope objective. There are a variety of methods of autofocus including measuring distance via sound, laser or image processing. Typical autofocus systems are configured to find the best focus on an object of interest in an image via a focus score or figure of merit. Autofocus typically scores sharpness of an image by looking for regions of great contrast. Typical focus scores ignore noise. For example, such autofocus systems find features, such as horizontal lines, of a prominent object in order to focus on the object. However, when a transparent sample being viewed by a microscope has very small multiple objects of interest on or near the surface of the sample while having other larger objects (such as labels and/or scratches) that are spatially larger and are substantially above or below the surface, the best focus is often ambiguous or incorrect to existing autofocus techniques. In such instances, conventional autofocus techniques may create a bimodal focus score resulting in the multiple objects of interest on or near the surface being out of focus. Because of the difficulty of conventional autofocus technologies to focus on a surface of a sample, new autofocus systems and techniques are desired.